The present invention relates to hand held nibbling machines and, more particularly, to such machines in which the tool mounting assembly is releasably mounted in the drive head.
Hand held nibbling machines are desirably employed for making cutouts in sheet metal and plate workpieces. It is desirable that such hand held nibbling machines utilize a tool mounting assembly carrying the die in spaced position relative to the lower end of the punch and providing a throat therebetween. These tool mounting assemblies must provide a reasonably rigid connection supporting the die and still be readily interchangeable in the drive head.
In Bitzel U.S. Pat. No. 3,847,049, such a hand held nibbling machine has the tool assembly secured in the drive head by threaded pins or the like which extend through openings in the drive head and which are removable to effect disassembly. Various types of connections between such threaded pins and the openings in the drive head are known.
Securing the threaded pin with a cross pin or similar connector has the disadvantage that there is a risk of its breaking under high stress, since all of the forces are channeled through this part into the housing. During nibbling, very high forces occur which put extraordinarily heavy stress on the connecting pieces. As a result, this construction should only be used in machines used to process work pieces which do not require very high nibbling forces. To accommodate greater nibbling forces, the upper end of the tool mounting assembly has been threaded and screwed into a corresponding threaded recess in the drive head. Thus, greater forces can be accommodated in the housing corresponding to the smallest circular cross section of the threaded connection pin.
However, the punch and die are subject to some wear and tear, and they have to be disassembled often to be sharpened or changed. Threading the tool mounting assembly in and out of the drive head is very time consuming. Another disadvantage of this construction is that rotating the tool mounting assembly relative to the drive head to nibble in another direction is possible only at various settings of the cutting edge of the die because of the pitch of the thread.
It is an object of the present invention to provide a novel hand held nibbling machine in which there is optimum transfer of the forces into the drive head and an engagement which enables rapid change of the nibbling tools.
It is also an object to provide such a nibbling machine which may be fabricated readily from durable components.
Another object is to provide such a nibbling machine in which the orientation of the throat relative to the drive head may be readily changed.